This invention relates to a self-activated, load-independent and level-regulating spring device.
For a long time there has been a continuous need in widely different fields of technology for reliable, inexpensive and technically uncomplicated self-activated, level-regulating spring devices. Such spring devices are needed especially, but in no way exclusively, in the automotive industry. The automotive industry requires such spring devices especially for wheel suspension and motor suspension. The costly construction of such self-activated, level-regulating spring devices has led to the result that such spring devices can only be used in isolated instances in vehicles of a high price range. In addition, the known spring devices have the disadvantage of not being unconditionally load-independent, unless their resiliency is controlled by a centralized control. This means that for each different type of vehicle, different spring devices have to be kept at disposal. This results in high storage and inventory costs not only for automotive manufacturers but also for car repair garages.
Motor suspension especially requires soft, that is, flat operational spring characteristics for the spring device to be used. The required spring device thus needs to make available large spring paths of travel for predetermined loads. In view of the resilient spring devices used nowadays, such spring devices need to have relatively large dimensions in order to fulfill the aforementioned requisites to ensure a reasonable life for the elastomer and to prevent overloading or overstressing of the elastomer during operation. However, at the same time, it is required that such spring devices have approximately the same spring resiliency with different loads, thus even with differing heavy drive mechanisms for substantially the same types of vehicles, accordingly, rubber-elastic spring devices should, with basically the same dimensions for different loads, have the same soft spring characteristics. This problem, in practice, nowadays, is solved by providing rubber spring devices with substantially the same dimensions, but in each case with differing hardnesses corresponding to the load, and which, for this reason, have widely differing spring characteristics. It can readily be seen that this practice requires not only expensive storage and inventory, but also opens up the possibility for numerous mixups and confusion. It has frequently happened that heavier motors have been supported on spring devices that were too soft or, vice versa, and that light motors have been suspended on spring devices that were too rigid.
In view of this state of the art, this invention has as an object to provide a self-activated and, above all, a load-independent, level-regulating spring device for any desired purpose, especially, however, for the automotive industry, and particularly for drive mechanisms and wheel suspensions, which, despite being provided with load-independent level regulation independent from load, has the same soft spring resiliency and defined spring paths as well as improved life, turns out in the long run, to be inexpensive as its higher price is more than compensated for when it is compared to simple rubber spring devices by the savings that result from lesser storage and inventory expenses and the lack of complaints.
To obtain this objective, this invention provides an automatic, load-independent, level-regulating spring device of the aforementioned type. The spring device of the present invention distinguishes itself, in substance, by a separation of the functions of cushioning and pumping. The entire cushioning or spring loading effect is taken over by a hydraulic spring chamber that is activated hydraulically by a pump which, in turn, does not fulfill any spring-loading function. The pump is not driven by outside energy sources, being rather activated through the relative motions between the two parts which move relative to each other, e.g. the parts that are to be spring-loaded or cushioned relative to each other. This type of drive of the pump chamber is acheived in that the pump chamber, that is, the displacement or compression chamber, is connected to one of the parts to be cushioned against each other, while the pump piston in each case is activated by the other part. Such activating may take on various forms, for example through an articulated piston rod, or may be a flexible connection, for instance a spring biased pump piston biased against a surface of the part to be impacted. Such a spring impacting of the pump piston, however, only serves the purpose to maintain the pump piston always biased on one of the two parts to be cushioned against each other and may not serve the purpose of shock absorption.
With this type of coupling of the pump between the two parts to be cushioned against each other, the relative position of the pump piston in the pump, that is, the displacement or compression chamber of the pump will always correspond to the distance of the two parts to be cushioned against each other, thus "reproducing" this distance according to the theory of the control system. Through the release of a bypass connection to the supply recipient of the hydraulic fluid above a predetermined limiting position, thus above a predetermined limiting distance of the two parts to be cushioned against each other, the opening of the bypass connection causes a decrease in pump pressure. The spring chamber thus is not impacted with pressure fluid any further and thus will not enlarge the distance of the two parts to be cushioned against each other. This distance will only be enlarged again, if, for instance, leakage arises on the pressure side of the hydraulic system that will reduce the distance of the two parts to be cushioned against each other.
It is of special advantage in practice if the whole pump is assembled inside the spring chamber itself. The whole system can thus be enclosed hermetically by the spring chamber. Especially in this case, according to one embodiment of the invention, the connecting channel and the second control valve are preferably formed in the pump piston itself in the case of a sliding piston pump and thus in the piston slider.
The spring device may be of radial or, yet, of axial construction. The concepts "radial" and "axial" refer to the main components of the forces to be acted upon and to be cushioned.
The advantage of the automatic, level-regulating spring device of the invention herein resides in the fact that the level regulation most of the time works load-independent to a large extent. Independently from the size of the load to be cushioned, the spring chamber will always be pumped up high enough to release the bypass connection to the supply chamber in the pump chamber. The spring device follows exactly defined spring paths. In other words, the spring device of the present invention makes it possible to achieve about the same spring action or behavior and identical level regulation with the same type of construction for differing loads.
Furthermore, since the spring chamber is supported by the pumping-up effect and unloaded by the springy material, it is possible to achieve long-life characteristics with the utilization of an elastomer as raw material for the cushioning of the spring chamber, which is independent from the so-called setting or behavior patterns and remains unaffected by fatigue of material and overstress of material which are frequently observed in traditional rubber spring devices.
The damping spring device, which can also be designated as a spring dampening device has the advantage that as the shocks or impacts grow stronger, the bearing is lifted with a greater amplitude of movement against the elastic stop, being hardened thereby, which causes the desired quieting down of the masses to be cushioned against the non-cushioned masses. Seen in its totality, the spring device of the present invention thus represents a hydraulically damped device.
In one embodiment in which the pump is, in essence, assembled in the supply chamber, a simplification is achieved by the fact that a single oblique or angular channel establishes a direct connection between the spring chamber and the damping chamber with the supply chamber. By the oval formation of the opening of the oblique channel leading to the supply chamber and the cross-sectional configuration of the oblique channel, throttling effects are achieved that permit a direct connection. By forming the pump piston with a larger cylinder diameter in the direction of the pump compartment and a smaller cylinder diameter in the direction of the rounded head area, it is possible to close off the direct connection to the spring chamber over the oval opening on an intake pulse so that the hydraulic fluid is drawn largely from the supply chamber alone. The type of construction of the pump in the supply chamber, however, also makes it possible to select a spring with lower spring action for impacting the pump piston, since post-guidance of the pump piston in the supply chamber is made easier. As the pump is assembled directly in the supply chamber, it will not be necessary to install a connecting passage in the form of a third connecting passage, which in the intermediate phase of lifting of the pump piston is used to establish a free connection between the pump compartment and the supply chamber.
The invention will now be explained in more detail by examples of embodiments with reference to the accompanying drawings.